Harry Caul (Gene Hackman), a paranoid surveillance expert, is charged with the task of monitoring a couple's conversation and activities. Though Caul may be expert at surveilling others; there is ample evidence in the film that he has not taken basic measures to secure his own life from surveillance.
The film was released shortly after the Watergate scandal broke, and deals with issues of personal responsibility and the encroachment of technology on privacy.
The film is consistently listed on the Internet Movie Database's list of top 250 films, and has been selected for preservation in the United States National Film Registry.
The film won the 1974 Palme d'Or (Golden Palm) at the Cannes Film Festival.